Many existing trailer hitches implement a hitch ball and socket connection to provide a connection of a trailer to a vehicle for towing. The trailer hitch connected to the vehicle is generally a hitch ball of a certain diameter and having a certain shank diameter to carry a desired load. Common hitch ball sizes include ball diameters of 1⅞″, 2″, and 2 5/16″. Hitch balls usually include a shank that distances the hitch ball above the hitch and provides a threaded connection to the vehicle. Common shanks have a round cross-section and have 3/4″, 1″, or 1¼″ diameters. A user will select a hitch ball of a certain diameter and a shank of a certain diameter to achieve a certain towing load capacity.
A trailer generally includes a trailer hitch coupler that includes a socket that receives the hitch ball. The coupler also includes a mechanical device to bring a clamping member into contact with the bottom of the hitch ball. Common mechanical devices include a hand crank and a lever. When the mechanical device is disengaged, the clamping member is loose and the coupler can be lifted over the hitch ball. When the mechanical device is engaged, a clamping member is raised into contact or near contact to the bottom of the hitch ball securing the trailer to the hitch ball. The clamping device and the socket generally form an opening that is smaller than the hitch ball diameter to prevent the hitch ball from being disengaged from the coupler while towing. In one commonly used coupler, a hand crank or lever includes a hook or latch that locks the hand crank or lever in an engaged position while towing to prevent the accidental loosening of the hand crank or lever resulting in an accidental release of the clamp. As an additional safety measure, it is also common to further secure a lever latch with a pin or a padlock. The hitch ball and coupler assembly provides force transfer in both lateral and vertical directions and provides a pivot point allowing the vehicle to turn, bank, and yaw while towing the trailer and maintaining a secure attachment to the towing vehicle.
SAE International has specified classes of hitch and coupler connections to be certified to pull a trailer having a trailer Gross Vehicle Weight (“GVW”). The GVW is the total weight of the load carried by the trailer including the trailer weight. For example, Class 1 assemblies include all trailers that carry a GVW of 2000 lbs., Class 2 includes all trailers that carry a GVW from 2000 lbs to 3500 lbs., Class 3 includes all trailers that carry a GVW from 3500 lbs. to 5000 lbs.; and Class 4 includes all types of trailers with a GVW between 5000 lbs. and 10,000 lbs. The trailer hitch assembly of the hitch ball, shank, and coupler are generally selected to be able to tow trailers of a certain weight class. Generally, the larger the hitch ball and shank diameter, the greater the load that may be transferred through the trailer hitch assembly. A coupler is selected having a material thickness sufficient to transfer the pull force to tow the desired GVW of the trailer. Thus, using the correct combination of hitch ball, shank diameter, and a coupler is fundamental to the safe and effective towing of trailers carrying various loads.
One shortcoming in the prior art is that it is possible for a coupler configured for a larger sized hitch ball may be placed over a smaller hitch ball. For example, a coupler configured to receive a 2 5/16″ hitch ball to be placed over a 2″ or 1⅞″ diameter hitch ball. The coupler will also latch when a coupler configured for a larger hitch ball is placed over a hitch ball of a smaller size giving the operator the false impression that the trailer is securely coupled to the vehicle. This situation can be very dangerous. If the trailer hitch connection is subjected to a vertical force by hitting a bump, or even rapid deceleration, the trailer can become detached from the hitch ball as the ball diameter is smaller than the opening provided when the clamp has been engaged by the lever or other mechanism. If a trailer becomes disengaged from the hitch ball, serious property damage and personal injury is probable and even deaths have occurred as a result.
Thus, there is a need in the art for a trailer hitch coupler that senses the size of the hitch ball and prevents the lever from latching or the clamp from being fully engaged when the hitch ball is of a smaller size than the coupler is configured to receive to prevent a user from coupling a trailer to a hitch ball that is too small. There is a further need in the art for a trailer hitch coupler to provide the operator a visual signal of whether the coupler is receiving a hitch ball of the correct diameter.